Effect Of Keggin-type Phosphomolybdic Acid On Electro-catalytic Oxidation Of Methaonol

Over the past decade, the direct methanol fuel cells (DMFCs) have been considering as a promising power source for portable electronics due to their ease of handling, high-energy densities, and low operation temperatures and so on. Pt is the best catalyst for methanol electrooxidation in the DMFC. However, Pt electrocatalysts are easily poisoned by CO species during methanol electrooxidation. It is an important topic to achieve catalysts with high catalytic activity and CO tolerance in DMFC.In this work, PMo₁₂-Pt/C catalysts were synthesized by reflux method and using H₃PMo₁₂O₄₀ as dispersant and carbon black XC-72 as support, and characterized by transmission electron microscopy, X-ray powder diffraction and thermogravimetic analysis. The result shows that PMo-Pt/C catalysts have good dispersion and narrow size of 3⁴ nm. Meanwhile, cyclic voltammetric responses of as-prepared PMo-Pt/C show enhanced electrocatalytic activity than that of Pt/C.AuPt/C catalysts with Au:Pt atom ratio of 0:1, 1:1, 1:5 and 1:10 were prepared by microwave-irradiation method using carbon black XC-72 as support and characterized by transmission electron microscopy, X-ray powder diffraction and energy dispersive X-ray. The result shows that AuPt/C series are unalloyed bimetallic system. TEM shows that the particles have an average size of 4¹0 nm. Cyclic voltammetry was carried out in 0.5 M H₂SO₄ + 1 M CH₃OH + x M H₃PMo₁₂O₄₀ to investigate the CO tolerance during methanol electro-oxidation. It is found that AuPt/C catalysts exhibit better CO tolerance than that of Pt/C and the If/Ib values (to evaluate the tolerance of catalyst to CO poisoning) are increased from ⁰.7 to ¹.2. The If/Ib values will increase with increasing H3PMo12O40 concentration in support electrolyte solutions and Au content in AuPt/C catalysts, but the catalytic activity to methanol electrooxidation slightly decreases. Besides, methanol electrooxidation of the Pt-modified Au (Pt-on-Au/C) catalyst was investigated in 0.5 M H2SO4 + 1 M CH3OH +x M H₃PMo₁₂O₄₀. It is found the Pt-on-Au/C catalyst shows higher electroactive surface area than that of AuPt11/C, and the peak current density (If) of methanol oxidation is as high as twice than that on AuPt11/C.